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10.02.2007 - DEQ pF Department of Environmental Quality __0 H; ; o regon Northwest Region Portland Office 2020 SW 4th Avenue,Suite 400 Theodore Kulongoski,Govemor Portland,OR 97201-4987 (503)229-5263 1859 FAX(503)229-6945 TTY(503)229-5471 October 2, 2007 Chris Breemer GeoEngineers 15055 SW Sequoia Parkway, Suite 140 Portland, OR 97224 Re: Review of Draft Human Health and Ecological Risk Assessment Tigard Library, ECSI#4063 Dear Chris: The Department of Environmental Quality(DEQ)has reviewed the Draft Human Health Risk Assessment and Level I and Level II Ecological Risk Assessment dated August 8, 2007 for the Tigard Library Site in Tigard, Oregon. DEQ has the following comments on the report: 1. Page 2, first paragraph: Beginning early in the report on page 2 and carried through the report (Section 4.4.1, etc.), is the assertion that Fanno Creek and offsite areas are not part of the locality of facility(LOF). The basis for this assertion, in part, is that the orchards at the site were on the northern part of the property and the property slopes to the North. The off-site orchards are indicated as the only source of arsenic contamination. While DEQ concurs that the primary source of contamination appears to have been from offsite, insufficient information is available to support a decision that contaminated soils on the property are not a current source to Fanno Creek. It is possible that the accumulated arsenic on the property may be entering the creek through the two storm water pathways —the newly-modified swale leading through the old pond, and the new Pinebrook Stream pathway through the wetland areas. The broad flow path to the north of the property is much less distinct as a discharge point to the stream. We agree that the LOF does not need to include upgradient properties and Hall Boulevard, though it should include Wall Street and the area encompassed by the stream realignment and wetlands work accomplished this summer. The LOF should include Fanno Creek, until the two potential stormwater pathways are adequately evaluated to determine if they represent a current source to Fanno Creek. If these pathways do represent a current source or likely potential source, DEQ would require the City to implement appropriate source control measures. 2. Page 2, Section 2.2, second paragraph: The Pinebrook Stream is described as a seasonal stream. However, it had a consistent base flow that had to be handled throughout the dryer-than-normal construction season this summer. 3. Page 3, Section 4.2: nature and extent discussion. This discussion on the depth profile of arsenic is an important one for both risk assessment and any future remedial action workplan. The assertion that contamination is limited to the upper 2-3 feet should be supported here by referencing a data summary table which shows summary statistics by depth. All the data points need not be presented but a summary table with minimum, maximum,mean, median, and sample numbers at each depth interval would better support conclusions regarding depth of impacted soil, limited mobility of arsenic and lack of impacts to groundwater. 4. Page 4, Section 4.3: The selection of arsenic as the sole COI should be supported here by referencing earlier reports that evaluated site history and use, and present a summary of the sampling results for other constituents, as appropriate. 5. Page 5, Section 4.4.5: The determination that groundwater has not been significantly impacted is based on arsenic concentrations attenuating with depth, and a statement that arsenic mobility is "limited"in the subsurface. DEQ agrees that this is likely the case, but these conclusions should be better supported. DEQ recommends adding this additional support in the form of one or more the following additions: 1)Presenting summary of site soil data(see Comment 3), 2)References to primary literature and EPA guidance supporting limited mobility and soil binding of arsenic, and 3)Doing some simple calculations using distribution coefficients (Kds) for arsenic in soil to demonstrate relative partitioning between soil and water phases. Providing this additional support will support a conclusion of no groundwater impacts, and allow a determination that the groundwater to surface water pathway is incomplete. 6. Page 6, Section 5.1: If soils beneath paved or capped portions of the site are not included in the risk evaluation, a soils management plan and institutional controls will likely be necessary for the final remedy. However, if these are included in the risk assessment and no unacceptable risk is documented(construction & excavation worker), no institutional controls would be needed. 7. Page 6, Section 5.1.1: It would be helpful to link the depths evaluated to the future remedial action workplan. On inspection of the data presented, it appears that the depth where arsenic exceeds unacceptable risks may be limited to 0-2 feet. The data from all 195 samples should be provided in an excel file to help in review. DEQ did prepare box plots (shown below) on the data from the April 2007 sampling event,but this is not the complete set used in the risk assessment. The April 2007 data appear to show that below 2 feet the arsenic level may be within background, but the variance is high, so the picture is unclear from this preliminary review. No sample below 3 feet was greater that 8.5 ppm, which is within the range of background. An evaluation of the complete data set sorted by depth and location collected would likely clarify the situation. If the final remedy were to ,include scraping and removal, this decision could significantly impact the volume required. If capping and institutional controls are implemented then this is less important. However, the described evaluation by depth should be performed and presented. JL.�iK i . r � � R t 0tSC gntc , g t i 4 E 4<2E �,• •& e f 5 X w s f- �i JJi,j" S Fre ... a� AM f Mg } F <- . Rrsr s x Arsenc€2 Arsernc(3 F f#rseruc(4-5) Arserrie(&7) 8. Page 7, Section 5.1.3: The data sets used should be provided so DEQ can review the EPCs. 9. Page 9, Section 5.3: The recent construction incorporated the existing pond into the storm drainage pathway as a prominent feature, although diversion of the base flow of the Pinebrook Stream will make this pond much more seasonal than it may have been historically. Some of the highest levels of arsenic contamination are near the pond, and pond water and sediments have not been sampled. There needs to be a basic evaluation of the risks within the pond aquatic habitat and sediments, as well as consideration of whether overflows from the pond would pose concerns as a source to Fanno Creek, as previously described (Comment 1). Similarly, the realigned Pinebrook Stream needs to be evaluated as a potential source of arsenic to Fanno Creek. 10. Page 9, Section: 5.3.2: The PEC is a relevant criterion. However, the maximum concentrations from erodable soils should be used,not the 90th UCL EC. This would then identify any localized areas where concentrations range from 33 to 113 ppm that could pose a source to the wetland or Fanno Creek by erosion. 11. Page A-6, Appendix A, Section 2.7.3. The SLV is the same for both plants and birds so both are exceeded, not just the plant SLV. Also, the maximum should be used for comparison to the PEC. :Jl:1 iK Identified Data Gaps There are a few data gaps that need to be considered as the risk assessment is finalized: A. The pond needs to be adequately characterized to provide for a basic risk assessment for the pond aquatic habitat and sediments. B. The overflow from the pond to Fanno Creek needs to be evaluated to determine whether this storm water pathway is a potential source of contamination to Fanno Creek. C. The realigned Pinebrook Stream needs to be adequately characterized to determine whether this pathway is a potential source of contamination to Fanno Creek. D. The southern portion of the site where construction took place this summer needs to be verified in its characterization. A post-construction report needs to be submitted that documents the changes made, what soils were removed from the site, what soils were relocated, and what the actual conditions are in relation to arsenic contamination. Key questions would include how the areas with elevated arsenic beneath pavement or soil cover were handled when those areas were disturbed or excavated. My observations periodically during the work suggest that there was appreciable disturbance to some of the soils for utility trenches, etc, that may have modified the normal soil profiles. Unless these areas were carefully monitored and documented during the work, we recommend verification sampling to ascertain the levels remaining in the shallow soils. We also recommend verification sampling of the shallow materials along the Pinebrook Stream pathway, including the sediments that have been deposited behind the berms (related to comment C above). We look forward to discussing these comments with you and the ongoing steps toward a final remedy for the site. Please contact me directly at (503) 229-6900 if you have questions. Sincerely, Loren G. Garner, Project Manager Northwest Region Cleanup Section Cc: Keith Johnson,DEQ Dennis Koellermeier City of Tigard 13125 SW Hall Blvd. Tigard, OR 97223 M Q4K1